The factor being tested is the variable. There are two types of variables, independent and dependent. The independent variable is the factor being changed by the scientist or the person controlling the experiment. The dependent variable is the thing that gets changed due to the changing of the independent variable. The dependent variable cannot be changed physically by the person doing the experiment.
The correct answer is hydronephrosis. Distention means being enlarged or swollen due to internal pressure. In this case, the internal pressure would be urine collecting in the kidney. This occurs when the urine is unable to drain from the kidney to the bladder due to an obstruction. Contrary to common belief, hydronephrosis is not a disease itself, but is instead is the result of a disease.